Mentha arvensis Linn. var piperescens. Holmes (menthol or Japanese mint) is an industrial crop that is widely cultivated for its essential oil from which menthol is purified by crystallization through freezing. Menthol and other terpenoids present in the dementholated oil of Mentha arvensis are variously used in the food, perfumery and pharmaceutical industries. In the varietal improvement programme the genetic alternations leading to enhancement in the tolerance against pest and disease and improving other adaptive characters determining the yield and quality of essential oil is most desirable. Insect tolerance is desired particularly against Spilarctia obliqua in mentha, which is the most damaging pest of mints in India. Since the mints are of considerable interest to the industrial world, selection programs for the isolation of desirable clones with improved terpene accumulation and suitable agronomic traits are being pursued in several laboratories. However, due to the inherent problem of seed setting in mints, conventional breeding programmes are severely hampered. In vitro high efficiency procedures for cell and callus cultures and shoot regeneration from axillary buds and leaf explants have been reported in some species of the genus Mentha, especially the commercially important species M. piperata and M. spicata. 
However, in M. arvensis mostly the media used have permitted shoot proliferation from limited explants such as nodes, terminal and axillary buds and distal segments of leaf petiole at relatively low levels of efficiency. Attempts to develop new varieties or genotypes by alternative methods like clonal selection, mutation breeding and somaclonal variation have been followed in mints (S. P. S. Khanuja, A. K. Shasany, S. Dhawan, S. Kumar, Rapid procedure for isolating somaclones of altered genotypes in Mentha arvensis. J Med. Aroma. Plant Sci. 20 (1998) 359–361.). The applicants have reported high efficiency protocols for rapid detection and selection procedure for development of somaclonal variants through molecular approaches in Mentha arvensis (S. P. S. Khanuja, A. K. Shasany, S. Dhawan, S. Kumar, Rapid procedure for isolating somaclones of altered genotypes in Mentha arvensis. J Med. Aroma. Plant Sci. 20 (1998) 359–361). We have also successfully defined the conditions and media to restrict the emergence of somaclonal variation for stable micropropagation purposes (A. K. Shasany, S. P. S. Khanuja, S. Dhawan, U. Yadav, S. Sharma, S. Kumar, High regenerative nature of Mentha arvensis internodes. Journal of Biosciences 23 (1998) 641–646.).
In the present invention, the applicants have utilized the already reported protocol (S. P. S. Khanuja, A. K. Shasany, S. Dhawan, S. Kumar, Rapid procedure for isolating somaclones of altered genotypes in Mentha arvensis. J Med. Aroma. Plant Sci. 20 (1998) 359–361.) to generate and capture the somaclonal variations in larger frequencies. We, then screened the somaclones for their tolerance to Spilarctia obliqua by devising a novel method for rapid and dependable selection of tolerant clone(s) right at the tissue culture stage. Further the tolerant plants, which survived were tested for their stability, essential oil, menthol content and biomass yield. Consequently, the plant GRB2-18 was selected for unmatchable vigor of shoots, higher menthol production and increased insect tolerance through field evaluation.